Composite structural element and method of making the same



R. BOFINGER Jan. 5, 1965 COMPOSITE STRUCTURAL ELEMENT AND METHOD OF' MAKING THE SAME Filed Oct. 2, 1962 United States Patent itice 3,164,110 Patented Jan. 5, 1965 COMPSITE STRUCTURAL ELEMENT AND METHQD F MAKING TIE SAlVlE v Rudolf Bollinger, Ilsfeld, near Heilbronn (Neckar), Germany Filed Get. Z, 1962, Ser. No. 227,871

Claims priority, application Germany, Oct. 6, 1961,

B 64,270 S Claims. (Cl. S-161) The present invention relates to a composite structural element and to a method of making the same. More particularly, the present invention is concerned with a double-walled structure forming pieces of furniture or supporting parts thereof and the like.

Itis an object of the present invention to provide pieces of furniture, particularly supporting pieces of furniture which then may be upholstered or otherwise further as'- sembled, which will be of sturdy construction and light weight, and which may be produced in a simple and economical manner.

It is a further object of the present invention to produce such pieces of furniture or supporting portions thereof which may be of irregular or complicated configuration so that it would be difficult or impossible to produce the same by extrusion or pressing methods.

Other objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in view, the present invention contemplates in a piece of furniture, in combination, a lower shell formed of synthetic sheet material and including a peripheral r'un portion and a plurality of downwardly extending hollow supporting portions, an upper shell formed of synthetic sheet material and including a peripheral portion contacting the peripheral rim portion of the lower shell and connected to the lower shell at the rim portion and in the region of the hollow supporting portions, the upper and lower shells defining therebetween a free space, and reinforcing means located in the free space filling the same at least partly and contacting the upper and lower shells.

According to a preferred embodiment, the present invention is concerned with a piece of furniture which comprises in combination, a lower shell formed of reinforced synthetic sheet material, said lower shell including a substantially horizontally extending inner portion, an upwardly extending peripheral rim portion continguous with the inner portion, and a plurality of hollow supporting portions open at their lower ends extending and tapering downwardly from the inner portion spaced from the rim for closing the lower open ends of the downwardly extending hollow portions.

It is also within the scope of the present invention to provide in -a method of producing a double-walled piece of furniture, the steps of forming in a mold a lower shell of hardenable reinforced synthetic sheet material, forming in a mold an upper shell of hardenable reinforced synthetic sheet material adapted to be superposed upon the lower shell so as to define between the superposed upper and lower shells a closed free space, placing a layer of reinforcing material on the lower shell in such a manner that the reinforcing material will be located in the free space and will contact the upper shell when the same is superposed upon the lower shell, superposing the upper shell upon the lower shell with the reinforcing material thereon while the upper and lower shell are still in hardenable condition, and allowing the superposed shells to harden while in contact with each other, thereby forming an integral structure consisting essenti-ally of the hardened superposed shells with the layer of reinforcing material therebetween.

Preferably, the two or more shell portions of the furniture structure or the like of the present invention are produced in two-part molds, by r'st wetting the inner face of the matrix with a separating agent, then placing the desired coloring agent `and a synthetic resin mass including a suitable curing agent into the mold. Preferably the resin will be an unsaturated polyester, and a layer of such unsaturated polyester including a curing agent is applied to the matrix in la thickness preferably of less than l mm., most preferably between 0.3 and 0.5 mm. This polyester -layer may be applied by brushing or spraying or other suitable means known in the art. Thereafter, a reinforcing glass liber mat, fabric or layer is placed onto the not yet hardened free face of the polyester layer in the mold and then another polyester layer is applied to the free face of the reinforcing layer, for instance by spraying or brushing. The second polyester layer will also include -a suitable curing or activating agent. The thus-formed composite, and as yet unhardened, structure is then reduced in thickness by pressing or rolling to the desired thickness of preferably below 2 mm. A layer of reinforcing material, for instance porous synthetic material of considerable hardness and strength, or a honeycomb structure which may be formed of paper, is then placed onto the thus-formed lower shell while the saine is still in unhardened and deformable condition, and then portion, a layer of reinforcing material located on the inner portion and extending upwardly therefrom for a predetermined distance, the reinforcing layer being formed with openings therethrough located in the region of the hollow supporting portions, an upper shell formed of reinforced synthetic sheet material and including an inner portion and a peripheral flange portion continguous with said inner portion the peripheral ange portion contacting and adhering to the peripheral rim portion of the lower shell so that the inner portion of the upper shell will be superposed upon the inner portion of the lower shell spaced therefrom the predetermined distance and thus contacting the layer of reinforcing material, the upper shell -also including a plurality of hollow downwardly extending and tapering portions 4open at their lower ends extending through the openings in the layer of reinforcing material into the hollow supporting portions of the lower shell substantially to the lower ends thereof and adhering to the inner faces of the tapering hollow supporting portions thus being supported by the same, and closing means an upper shell which has been formed in a manner similar to that of forming the lower shell, however, preferably on the outer face of a mold (patrix) is then placed onto the lower shell `and on the layer of reinforcing material which thus will be interposed between the still actively adhesive upper and lower shell. The upper and lower shells will contact each other along their peripheral rim or flange and `also at their downwardly extending and tapering hollow portions. Presure is now applied and maintained until the two shells, of,A for instance, reinforced, hardenable polyester resin have hardened and thus have been firmly adhered to each other.

The method of the present invention is particularly advantageous in connection with forming pieces of furniture such as chairs or couch frames which are formed with upwardly flaring, or downwardly tapering, legs which extend downwardly from the lower shell, continuous with the same, as illustrated in the drawing.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a top plan view of a couch frame according to the present invention; and v Y FIG. 2 is a cross sectional view taken along line 2-2 of FIG. l. n

Referring now to the drawing, it will be seen that the couch frame consists of upper shell 1 and lowershell 2 both of which are formed with glass reinforced unsaturated polyester resins` and are produced as described further above. A honeycomb reinforcing structure 3 is interposed between upper shell 1 and lower shell 2 and is formed with openings in the region of the hollow supporting portion of lower shell 2 and the downwardly extending hollow portions of upper shell 1. The upper and lower faces of honeycomb structure 3 adhere to the adjacent faces of upper and lower shells 1 and 2. Upper and lower shells 1 and 2 are furthermore firmly adhered to each other along peripheral rim portion 5 of lower shell 2 and iiange portion 4 of upper shell 1.

The legs of the couch may be formed by the superposed downwardly extending hollow portions of shells ll and 2, which downwardly extending hollow' portions are indcated by reference numerals 1 and 2'. The lower open ends of superposed portions 1' and 2 are preferably closed, for instance by insertion of rubber Stoppers 6. During assembly of upper and lower shells 1 and Z, the trumpet shaped downwardly extending hollow portions 1 oi' upper shell 1 will be inserted through the openings in reinforcing layer 2 into the tapering downwardly extending hollow portions 2' of lower shell 2. Preferably, portions 1 and 2' will be pressed against each other during the curing and hardening of the two shells so that the two shells will be firmly adhered to each other along peripheral rim and flange portions 4 and 5 and at least at the lower part of the downwardly extending hollow portions 1' and 2.

Upper shell 1 is preferably formed on a mold surface which is so positioned that portions 1 of upper shell 1 will extend upwardly while being formed on the mold surface. During pressing of the upper shell 1 forming composite layers of polyester resin and reinforcing glass fibers or fabric, excess, curing agent containing, liquid synthetic resin will collect in the trough-like flange portion 4. According to a preferred manner of producing the structure of the present invention, glass fibers will be introduced into the trough-shaped portion of ange 4 so as to form a mixture of liquid polyester and reinforcing material therein. When then, after interposition of reinforcing layer 3, the Vlower shell 2 is superposed upon shell 1, so that the now superposed tapering hollow portions will extend upwardly, intimate contact wl be established' between rim 5 and the groove formed in flange 4 with polyester resin and iberous reinforcing material therein. The contacting rim and flange portions 4 and 5 are then rmly pressed against each other until the resin has hardenedA In somewhat similar manner, however, generally without applying additional reinforcing fibers, hollow tapering portions 1 and 2 are pressed against each other and pressure is maintained until these portions have hardened. v

Ifdesired, the open ends of thesuperposed hollow portions 1 and Z' may be closed by any suitable wall, for instance, as illustrated, by rubber Stoppers 6. Rubber stopper 6 will press portion 1 against portion 2 and thus increase the firm adherence between these two portions.

It is desirable but not required that reinforcing layer 3 is adhered to the adjacent faces of shells 1 and 2.

Sufficient mechanical strength is maintained according to the present invention with shells of glass fiber reinforced synthetic resin, preferably unsturated polyester resin, lhaving a thickness which may be less than 2 mm. so that it is possible according to the present invention to produce furniture structures of great strength with a relatively small quantity of synthetic resins.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a piece of furniture, in combination, a lower shell formed of synthetic sheet material and including a peripheral rim portion and a plurality of downwardly extending hollow supporting portions; an upper shell formed of synthetic sheet material and including a peripheral por tion directly contacting said peripheral rim portion of said lower shell and directly connected to said lower shell at said rim portion and including also a plurality of downwardly extending portions arranged in the region of said hollow supporting portion of said lower shell and directly supported by said lower shell in the region of said hollow supporting portions, said directly connected upper and lower shells defining therebetween a free space; and reinforcing means located in said free space filling the same at least partly and contacting said upper and lower shells.

2. ln a piece of furniture, in combination, a lower shell formed of reinforced synthetic sheet material and including a peripheral rim portion and a plurality of downwardly extending and tapering hollow supporting portions; an upper shell formed of reinforced synthetic sheet material and including a peripheral portion directly contacting said peripheral rim portion of said lower shell and directly connected to said lower shell at said rim portion and including also a plurality of downwardly extending portions arranged in the region of said hollow supporting portion of said lower shell and directly supported by said lower shell in the region of said hollow supporting portions, said directly connected upper and lower shells dehning therebetween a free space; and reinforcing means located in said free space filling the same at least partly and contacting said upper and lower shells.

3. In a piece of furniture, in combination, a lower shell formed of synthetic sheet material and including a peripheral rim portion and a plurality of downwardly extending and tapering hollow supporting portions; an upper shell formed of synthetic sheet material and including a peripheral flange portion directly contacting and adhering to said peripheral rim portion of said lower shell, and also including a plurality of downwardly extending and tapering portions located in said hollow supporting portions of said lower shell in direct contact with and thus being supported by the inner faces thereof, said directly connected upper and lower shells defining therebetween a free space; and reinforcing means located in said free space filling the same at least partly and contacting said upper and lower shells.

4, In a piece of furniture, in combination, a lower shell formed of synthetic sheet material and including a peripheral rim portion and a plurality of downwardly extending and tapering hollow supporting portions; an upper shell formed of synthetic sheet material and including a peripheral flange portion directly contacting and directly adhering to said peripheral rim portion of said lower shell, and also including a plurality of downwardly extending and tapering portions nesting in said hollow supporting portions of said lower shell contacting and directly adhering to the latter, said directly connected upper and lower shells defining therebetween a free space; and reinforcing means located in said free space filling the same at least partly and contacting said upper and lower shells.

5. In a piece of furniture, in combination, a lower shell formed of reinforced synthetic sheet material, said lower shell including a substantially horizontally extending inner portion, an upwardly extending peripheral rim portion contiguous with said inner portion, and a plurality of hollow supporting portions extending and tapering downwardly from said inner portion spaced from said rim portion; a layer of reinforcing material located on said inner portion and extending upwardly therefrom for a predetermined distance, said reinforcing layer being formed with openings therethrough located in the region of said hollow supporting portions; and an upper shell formed of reinforced synthetic sheet material and including an inner portion and a peripheral flange portion contiguous with said inner portion said peripheral flange portion directly contacting and being directly connected to said peripheral rim portion of said lower shell so that said inner portion of said upper shell will be superposed upon said inner portion of said lower shell spaced therefrom said predetermined distance and thus contacting said layer of reinforcing material, said upper shell also including a plurality lof hollow downwardly extending and tapering portions extending through said openings in said layer of reinforcing material into said hollow supporting portions of said lower shell directly abutting against the inner faces thereof and thus being supported by the same.

6. In a piece of furniture, in combination, a lower shell formed of reinforced synthetic sheet material, said lower shell including a substantially horizontally extending inner portion, an upwardly extending peripheral rim portion contiguous with said inner portion, and a plurality of hollow supporting portions extending and tapering downwardly from said inner portion spaced from said rim portion; a layer of honeycomb reinforcing material located on said inner portion and extending upwardly therefrom for a predetermined distance, said reinforcing layer being formed with openings therethrough located in the region of said hollow supporting portions; and an upper shell formed of reinforced synthetic sheet material and including an inner portion and a peripheral flange portion contiguous with said inner portion said peripheral flange portion directly contacting and being directly connected to said peripheral rim portion of said lower shell so that said inner portion of said upper shell will be superposed upon said inner portion of said lower shell spaced therefrom said predetermined distance and adhering to said layer of reinforcing material, said upper shell also including a plurality of hollow downwardly extending and tapering portions extending through said openings in said layer of reinforcing material into said hollow supporting portions of said lower shell abutting against and directly adhering to the inner faces thereof and thus being supported by the same.

7. In a piece of furniture, in combination, a lower shell formed of reinforced synthetic sheet material, said lower shell including a substantially horizontally extending inner portion, an upwardly extending peripheral rim portion contiguous with said inner portion, and a plurality of hollow supporting portions open at their lower ends extending and tapering downwardly from said inner portion spaced from said rim portion; a layer of reinforcing material located on said inner portion and extending upwardly therefrom for a predetermined distance, said reinforcing layer being formed with openings therethrough located in the region of said hollow supporting portions; and an upper shell formed of reinforced synthetic sheet material and including an inner portion and a peripheral flange portion contiguous with said inner portion said peripheral flange portion directly contacting and directly adhering to said peripheral rim portion of said lower shell so that said inner portion of said upper shell will be superposed upon said inner portion of said lower shell spaced therefrom said predetermined distance and thus contacting said layer of reinforcing material, said upper shell also including a plurality of hollow downwardly extending and tapering portions open at their lower ends extending through said openings in said layer of reinforcing material into said hollow supporting portions of said lower shell substantially to the lower ends thereof and directly adhering to the inner faces of said tapering hollow supporting portions thus being supported by the same.

8. In a piece of furniture, in combination, a lower shell formed of reinforced synthetic sheet material, said lower shell including a substantially horizontally extending inner portion, an upwardly extending peripheral rim portion contiguous with said inner portion, and a plurality -of hollow supporting portions open at their lower ends extending and tapering downwardly from said inner portion spaced from said rim portion; a layer of reinforcing material located on said inner portion and extending upwardly therefrom for a predetermined distance, said reinforcing layer being formed with openings therethrough located in the region of said hollow supporting portions; and upper shell formed of reinforced synthetic sheet material and including an inner portion and a peripheral flange port-ion contiguous with said inner portion said peripheral flange portion directly contacting and directly adhering to said peripheral rim portion of said lower shell so that said inner portion of said upper shell will be superposed upon said inner portion of said lower shell spaced therefrom said predetermined distance and thus contacting said layer of reinforcing material, said upper shell also including a plurality of hollow downwardly extending and tapering portions open at their lower ends extending through said openings in said layer of reinforcing material into said hollow supporting portions of said lower shell substantially to the lower ends thereof and `directly adhering to theinner faces of said tapering hollow supporting portions thus being supported by the same; and closing means for closing the lower open ends of said downwardly extending hollow portions.

References Cited in the le of this patent UNITED STATES PATENTS 2,544,657 Cushman Mar. 13, 1951 2,802,766 Leverenz Aug. 13, 1957 3,091,497 Houser May 28, 1963 

1. IN A PIECE OF FURNITURE, IN COMBINATION, A LOWER SHELL FORMED OF SYNTHETIC SHEET MATERIAL AND INCLUDING A PEREIPHERAL RIM PORTION AND A PLURALITY OF DOWNWARDLY EXTENDING HOLLOW SUPPORTING PORTION; AN UPPER SHELL FORMED OF SYNTHETIC SHEET MATERIAL AND INCLUDING A PERIPHERAL PORTION DIRECTLY CONTACTING SAID PERPHERIL RIM PORTION OF SAID LOWER SHELL AND DIRECTLY CONNECTED TO SAID LOWER SHELL AT SAID RIM PORTION AND INCLUDING ALSO A PLURALITY OF DOWNWARDLY EXTENDING PORTIONS ARRANGED IN THE REGION OF SAID HOLLOW SUPPORTING PORTION OF SAID LOWER SHELL AND DIRECTLY SUPPORTED BY SAID LOWER SHELL IN THE REGION OF SAID HOLLOW SUPPORTING PORTIONS, SAID DIRECTLY CONNECTED UPPER AND LOWER SHELLS DEFINING THEREBETWEEN A FREE SPACE; AND REINFORCING MEANS LOCATED IN SAID FREE SPACE FILLING THE SAME AT LEAST PARTLY AND CONTACTING SAID UPPER AND LOWER SHELLS. 